Suppose two places are very similar. After I add one of them, is there a simple way to copy one onto the other location, rather than re-typing all the details?
And, would this be an appropriate way to indicate two widely separated entrances of a restaurant or store? Several times, recently, I have encountered a place, not on a corner, that spans a whole block and has entrances on both ends, on parallel streets.
That depends on the editor that you are using.
If you are using JOSM, you can:
place two nodes or ways, select them both, then add attributes, and those attributes will go into all the selected objects;
place a new object, do copy on the old one, then do paste tags on the new one;
copy the old object, paste it as a new object, and then move to the right place, possibly joining it to existing features; or
directly duplicate it and then place and join it.
Note that the copy is done by value, not references, so once done, you have to update both copies.
AFAIK, the procedures described by hadw are not available in the online editor (iD), which you might be using.
This is a feature that was requested awhile ago (https://github.com/openstreetmap/iD/issues/839 ) but has not been implemented yet.
To answer the second part of your question, one real-world feature such as a restaurant or store should only appear in the map once. Maybe the situation you described could be represented by drawing the place as a polygon (area), and tagging some of the polygon’s nodes as entrance? You can even distinguish between main and side entrances that way.
Our online editor iD supports copy&paste by CTRL+C and CTRL+V.
Actually, I use an app called Maps.me which SUCKS for editing, sucks for routing, and is barely tolerable for tracking.
But it doesn’t suck (unfortunately) for constantly finding things that aren’t at the location indicated, or paths/roads that don’t exist, or
paths/roads that do exist but aren’t shown, etc. So I would like to learn to use a better editor to fix these things after my walks and bike rides confront me with them.
A really easy to use editor is StreetComplete. It just ask you for names, surfaces, opening hours, etc.
I’ll look into that. Does it allow correction of a location?